This invention relates to an improvement on the replacement technique of a tire from the vehicle wheel, in more details, pertaining to such apparatus that enables the bead of even a tire, the ratio or nominal aspect ratio of which sectional height to the sectional width thereof is small, said nominal aspect ratio being expressed with the percentage of fivefold numerals, and the rigidity of which side portions is high, to be detached from the rim edge of the wheel not by manual labor, but by a mechanical operation in a safe and efficient manner and the same method.
The wheels of the vehicles for land transportation, on which tires are directly mounted without filling a tube inside, prevail over in the market. The replacement of such tubeless tire as mentioned above, in which a tire is detached from the wheel, requires hard manual labor and higher skill on the part of the operators in comparison with the replacement work of the tire with a tube filled inside, and is prone to injure the operators. Thus, various types of tire replacement devices have been developed to date to lighten the burden on the part of the operators as well as to secure their safety.
One example of such prior tire replacement devices is disclosed in Japanese Patent Registration No.2668318 entitled xe2x80x9cMethod for detaching a tire of small nominal aspect ratio from the vehicle wheel and the same apparatusxe2x80x9d in the name of the present inventor, which method comprises the steps of fixing a wheel round which a tire is placed on a certain turntable; compressing said tire from above so as to shove a tire bead into the setback portion of the wheel; inserting a steel lever between the tire bead and the rim edge of the wheel so as to squeeze out of the wheel the tire bead and to hang the bead onto the bead suspender while at the same time to revolve the turntable so as to detach the tire bead from the wheel.
However, for its sporty appearance""s sake, the recent passenger car tends to become short in height as if it touches the ground, due to which, a tire whose nominal aspect ratio is below 50% and the rigidity of which side portions is extremely high becomes popular. If such tire of small nominal aspect ratio as mentioned above is detached from the wheel by such prior tire replacement device as mentioned above, it not only requires hard labor on the part of the operators to squeeze out of the wheel a tire bead, but also it often occurs that a lever in use is displaced from the wheel so as to do damage on the latter or the operators get injured, which prior issues are to be solved by the present invention.
In view of the above inconveniences encountered with the prior art and in order to solve such prior issues as mentioned above, the present invention is to provide an apparatus for detaching a tire from the vehicle wheel and the same method, which apparatus and method enable a bead of even the tire of such small nominal aspect ratio as mentioned above, the rigidity of which side portions is high, to be detached from the rim edge of the wheel in a safe and efficient manner.
That is to say, the apparatus for detaching a tire from the vehicle wheel embodied in this invention is characterized in comprising a turntable which rotates by a driving portion and on the top surface of which a wheel, round which a tire is placed, is detachably mountable; an elevating rod disposed above said turntable such that it moves up and down to a destination; a tire bead separation shoe comprising a wedge portion to engage with a rim edge of the wheel so as to shove between said rim edge and tire bead and a tire bead fold-back portion disposed adjacent to said wedge portion; a thrusting rod provided with a claw at its tip end portion to insert said claw between the tire bead and the rim edge of the wheel and to squeeze out of the wheel the tire bead so as to move said bead onto the bead fold-back portion when the wedge portion of said shoe is shoved between the tire bead and the rim edge of the wheel and a boom arrangement to make said thrusting rod squeeze out of the wheel the tire bead.
Then, the method embodied in the present invention with the above apparatus in use is characterized in comprising the steps of lowering an elevating rod with regard to the wheel round which a tire is placed and which is fixed on a turntable so as to engage a tire bead separation shoe with a rim edge of the wheel and to shove a wedge portion between the rim edge of the wheel and the tire bead; operating a boom arrangement when said wedge portion is shoved between the tire bead and the rim edge of the wheel so as to insert a claw of a thrusting rod between the tire bead and the rim edge of the wheel and to squeeze out of the wheel the tire bead and to move the bead onto the tire bead fold-back portion of said separation shoe while revolving the turntable so as to detach the tire bead from the whole circumference of the rim edge of the wheel.
Hereinafter, the best mode for carrying out the invention is described in more details with reference to the accompanying drawings.